If $6a + 8b + 7c = -9$ and $2x + 3y + 3z = -6$, what is $-8x - 54a - 12y - 12z - 72b - 63c$ ?
Answer: $= -54a - 72b - 63c - 8x - 12y - 12z$ $= (-9) \cdot (6a + 8b + 7c) + (-4) \cdot (2x + 3y + 3z)$ $= (-9) \cdot (-9) + (-4) \cdot (-6)$ $= 81 + 24$ $= 105$